The present invention relates to a semiconductor device that is suitable for high density mounting, and to methods for manufacturing and mounting this semiconductor device.
In recent years, the rapid technological growth in the field of IC cards and memory cards has resulted in the need for thinner and more compact resin-sealed semiconductor devices to be mounted in the cards. In addition, stack type semiconductor devices achieved by stacking semiconductor devices over two stages or three or more stages have been proposed for memory modules and the like.
For instance, DIP (Dual Inline Package) semiconductor devices 100, one of which is illustrated in FIG. 15, may be employed to achieve a stack type semiconductor device 103 by stacking the semiconductor devices 100 one on top of the other and electrically connecting leads 101 provided at the side surfaces of the semiconductor devices 100 with solder 102 or the like, as illustrated in FIG. 16. In addition, a stack type semiconductor device 108 which is achieved by employing an SOJ (Small Outline J-bend Package) semiconductor device 106 having leads 105 bent in a "J" shape, as illustrated in FIG. 17, stacking a DIP type semiconductor device 100 on top of it and electrically connecting their leads 105 and 101 with solder 107 or the like, as illustrated in FIG. 18, has also been proposed. These semiconductor devices 106 and 100 are formed thin enough that the semiconductor device 108 has a height that is equivalent to that of one regular SOJ type semiconductor device. The stack type semiconductor devices 103 and 108, are each constituted by stacking semiconductor devices over two stages to achieve high density mounting and can store twice as much information.
However, since the leads 101 must be inserted at through holes to mount the stack type semiconductor device 103 illustrated in FIG. 16 at a substrate, double mounting cannot be achieved. Because of this, even though the semiconductor device 103 in FIG. 16 is constituted by multistage stacking, it is difficult to achieve high density mounting since double mounting is not possible.
In addition, in the stack type semiconductor device 108 illustrated in FIG. 18, the outer surfaces of the solder 107 connecting the leads 105 and 101 project out at the two sides to the left and the right. Because of this, the distance L107 between the outer surfaces of the solder 107 is greater than the distance L105 between the outer surfaces of the SOJ leads 105. Consequently, due to the projecting solder 107, the stack type semiconductor device 108 illustrated in FIG. 18 requires a greater mounting area compared to the mounting area required for mounting the semiconductor device 106 by itself, which represents an obstacle to achieving high density mounting. In particular, such an increase in the mounting area cannot be allowed when ultra high density mounting, in which the element footprint is under rigorous restriction, is to be implemented.